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  <title>Document</title>
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  <script>
    const ary = [100, 200];
    ary[0] = 'a';
    ary[1] = 'b';
    console.log(ary); // 可以更改数组内部的值，结果为['a', 'b']
    ary = ['a', 'b']; // Assignment to constant variable.
  </script>
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